Web conveying and treating method and apparatus

ABSTRACT

A web conveying apparatus having a plurality of pressure pads positioned transversely to the path of a web. Each pad has a surface generally parallel to the path of the web with a row of eyelid shaped openings extending along each longitudinal side of the pad. The eyelid openings are staggered transversely of the web and are oriented to direct the treating medium toward a region over the centerline of the pad surface.

United States Patent [1 1 [111 3,837,551

Schregenberger Sept. 24, 1974 [54] WEB CONVEYING AND TREATING 3,634,948 1/1972 Kobayashi 226/97 x METHOD AND APPARATUS 3,711,960 1/1973 Overly 226/97 X Inventor: Alex J. Schregenberger, Milltown,

Assignee: Midland-Ross Corporation, Cleveland, Ohio Filed: Aug. 22, 1973 Appl. No.: 390,498

Related US. Application Data Continuation-impart of Ser. No. 264,250, June 19, 1972, abandoned.

US. Cl 226/97, 34/57 A, 34/156 Int. Cl B65h 17/32 Field of Search 226/7, 97; 34/57 R, 57 A,

References Cited UNITED STATES PATENTS 1/1966 Wallin 226/97 FOREIGN PATENTS OR APPLICATIONS 835,251 5/1960 Great Britain 34/156 Primary Examiner-Richard A. Schacher [57] ABSTRACT A web conveying apparatus having a plurality of pressure pads positioned transversely to the path of a web. Each pad has a surface generally parallel to the path of the web with a row of eyelid shaped openings extending along each longitudinal side of the pad. The eyelid openings are staggered transversely of the web and are oriented to direct the treating medium toward a region over the centerline of the pad surface.

6 Claims, 3 Drawing Figures WEB CONVEYING AND TREATING METHOD AND APPARATUS This is a continuation-in-part application based on Schregenberger patent application Ser. No. 264,250 filed June 19, 1972, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to means and methods for supporting, treating and conveying articles, such as paper webs and metallic sheets, over a conveying path. During the conveyance of such an article, it is supported on air, or other gaseous medium, which is directed against or along the upper and/or lower surfaces of the material. When the material is conveyed in this fashion, there is frequently a problem of maintaining the material in a fixed vertical position relative to the pads without fluttering or wrinkle formation, particularly with thin or lightweight webs.

Many devices are available for the conveyance of a web through the use of a fluid medium. Virtually all of these devices utilize pressure pads in one form or another with their longitudinal dimension usually extending transversely relative to the path of the web. These pads generally fall into several types: those having a pair of elongate slots which extend lengthwise of the pad along each side of the upper longitudinal surface of the pressure pad; those having a plurality of openings in the upper surface of the pad; combinations of the first two; and those having a single slot or continuous nozzle along one side of the pressure pad which directs the treating medium across the upper longitudinal'surface of the pressure pad which is normally shaped to resemble an airfoil section.

The pressure pad of the type having elongated slots has certain shortcomings. First, they have proven satisfactory in the conveyance of relatively heavy, stiff ma terial such as metal strip but their performance is generally unsatisfactory when conveying light, flexible materials such as paper, especially at higher velocities of the gaseous medium. These light, flexible materials tend to flutter and wrinkle along the edges. This fluttering is caused by motion transversely of the web of the gaseous medium which is trapped between the converging jets of the gaseous medium and has to escape through regions adjacent the ends of the pressure pad. Second, the pressure pads of this type which utilize the Coanda effect (as described in Frost US. Pat. No. 3,549,070) to direct the jets toward the center of the pressure pad generally have lower heat-transfer coefficients for a given volume and pressure of gaseous medium than pressure pads which directly impinge the gaseous medium on the web surface, while still experiencing the problem of edge flutter due to escape of the gaseous medium transversely of the web. This lower heat-transfer coefficient is primarily due to the less turbulcnt flow of the gaseous medium when under the Coanda effect and a lack of direct impingement of the high velocity jet on the material surface. The edge flutter problem generally increases in severity as the web width increases. It is also expensive to fabricate the slots in this type of pressure pad with sufficientaccuracy to insure uniform heat transfer along the side-toside or transverse dimension of the web.

Conventional pressure-pads of the type having a plurality of openings on the upper surface of the pad, while generally having good heat-transfer characteristics, has

proven unsatisfactory for conveying light, flexible webs such as paper, because of web flutter and wrinkling. The good heat-transfer characteristics are primarily due to direct impingement of jets of gaseous medium on the web surface. Fluttering and wrinkling of the web are basically caused by the inability of this design to develop a sufficiently rapid rise in average pressure on the web surface as the web-to-pressure pad distance decreases.

Pressure pads of the type utilizing a single slot along one side of the pressure pad and an airfoil-shaped upper surface and utilizing the Coanda effect to direct the gaseous medium, generally have good web-carrying characteristics but are less efficient in terms of heat transfer than the other designs. This is primarily due to the less turbulent flow of the gaseous medium in the vicinity of the web in those designs.

Several other designs have been developed utilizing various combinations of the above types. For example, in one apparatus of the prior art, the pressure pads have two rows of eyelid shaped openings located adjacent to the centerline of the pressure pad and facing outwardly. Thus the gaseous medium is discharged obliquely toward the web and away from the centerplane of the pressure pad. With the openings thus ar ranged, a negative pressure area is created in the center of the pad which tends to pull the web toward the pressure pad. This concept decreases the tendency of the web to wrinkle by introducing a slight sinusoidal shape in the longitudinal direction but increases the tendency of the web to flutter by decreasing the net lifting force of the pad.

Thus, it is an object of this invention to provide a novel method and means for supporting sheet and weblike material by gaseous medium while the web is being longitudinally conveyed over a path in such a way that flutter and wrinkling of the web are avoided.

Another object ancillary to the foregoing object is to avoid fluttering and wrinkling of the edges of the web regardless of web width.

Still another object of the invention is to provide apparatus capable of establishing gaseous support of a web or sheet while in movement along a flat stream-like path which is easy and inexpensive to construct.

It is a still further object of this invention to provide means and apparatus which utilizes a gaseous websupporting medium as a means for heating the web at high efficiency and high web speed.

Other objects and a fuller understanding of the invention may be had by reference to the accompanying specification and claims taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a section of a web conveying apparatus which incorporates this invention;

FIG. 2 is a plan view of a portion of a pad used in the device shown in FIG. 1, showing the air jets which issue from the openings and their areas of impingement on the web; and

FIG. 3 is a cross sectional view of a pad taken along line 3-3 on FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, a portion of a supporting pad conveying device which utilizes the principle of this invention is shown generally at 10. This device has a plurality of transversely elongated lower pads 12 and upper pads 14 which can be of similar construction as shown, arranged with their lengths extending transversely of the web path and in a staggered relation with the lower pads proceeding lengthwise of the web path, as best seen in FIG. 1. These pads are of generally rectangular configuration in a plane facing the web path and normally made of sheet metal to provide a hollow housing. Each of the lower pads 12 is confluent with a lower duct 16 and each of the upper pads 14 is confluent with an upper duct 18. These ducts 16 and 18 supply air under pressure to the interior of the pads 12 and 14, respectively. Each pad has a slightly curved surface 20 which faces the path of a web 21. The surface 20 is convexly curved toward the web path in a direction lengthwise of the path. As shown, the surface 20 is sub stantially even in the sense that it is free except for openings 22, 24 of abrupt convexity or concavity, or substantial ridges or depressions. The general horizontal direction of the web is indicated by the arrow in FIG. 1. The term generally horizontal means herein that the web path may vary from the true horizontal at small angles of inclination therewith.

Referring now to FIGS. 2 and 3, each surface 20 has two rows of openings 22 and 24 extending longitudinally along each edge of the pads 12 and 14, i.e., at opposite sides of a longitudinal plane PP bisecting the surface 20. The openings 22 in one row are staggered relative to the openings 24 in the other row. Each opening 22 may be spaced longitudinally of the plane PP from the next opposite opening 24 by a distance, such as distance 25, measured between dotted lines 25a and 25b. The openings 22, 24 have an eyelid configuration, there being a lid 26 depending below the opening in an angular fashion and indented relation with the surface 20 to define a space 27 in sub-surface relation with the surface 20 contiguous with the interior of the pad. The periphery of each opening 22 and 24 at the plane of the surface 20 consists of a straight line portion 28 paralleling the edge ofthe pad 12 and a curvilinear portion 30 from which the lid 26 depends.

Warm or hot air is supplied from the ducts l6 and 18 to each of the lower and upper pads 12 and 14, respectively. The air is caused to flow through the space 27 intermediate the lid 26 and the upper surface 20 of each pad. The ratio of the lid opening 31 to the radius of curvature of the intersection of the lid 26 and the pad surface 20 is such that the Coanda effect cannot occur. Consequently, as the air passes through the openings 22 and 24, it forms cohesive jets which break away from the pad surface 20 in an oblique direction toward the bisecting plane PP of the surface 20 until they contact the web surface 21. Upon striking the web surface 21, the jets tend to spread both transversely and longitudinally on the web surface 21, creating areas of high velocity scrubbing of the web surface by the jets. FIGS. 2 and 3 illustrate the manner in which the airjets issue from the openings 22 and 24, and the dotted lines 33 on FIG. 4 indicate the boundaries of ovate areas of high velocity scrubbing on the web surface 21. The high velocity scrubbing action of the air jets on the web surface 21, combined with the escape path for air which has expended most of its kinetic energy between the openings on the opposite side of the pad, gives a higher heat-transfer coefficient than would be expected from pressure pads utilizing slots along the sides of the pad.

The transverse spacing 25 of the openings as shown by FIG. 2 is such that the areas of high velocity scrubbing indicated by dotted lines 33 overlap on their transverse edges. In these overlapping areas, the interaction of the opposing air jets converts most of the kinetic energy of this air to static pressure. This static pressure is transmitted to the bulk of the air between the pad surface 20 and the web 21, resulting in an increase in the lifting force or lifting pressure on the web 21. Thus, the lifting force of the pressure pad can be altered to suit the application by altering the transverse spacing 25 of the openings.

FIG. 2 shows that ample area is provided between the openings 22 for the air issuing from the openings 24 on the opposite side of the pad to escape. Thus the problem of air spilling out the ends of the pad transverse to the web as occurs with the slot-type pressure pads, and the resultant problem of fluttering and edge-wrinkling of thin, flexible webs, is eliminated without having to resort to end-seals or other devices which impede access to the pressure pads or which may damage the edges of the web. Air is exhausted from the positive pressure regions developed adjacent to the web primarily through the spaces between the pads 12 and 14. When the pads are in staggered arrangement as shown in FIG. 1 and the web is conveyed across the pads, the pressure created over the lower pads tends to support the web whereas the pressure created over the upper pads tends to prevent the web from being lifted. These opposing pressures provide a stabilizing influence. With the staggered or interposed relationship of the upper and lower pads in the direction of general web movement, the web travels along a generally sinusoidal path which tends to prevent wrinkles caused by tension.

In addition, the pressure pad of the preferred embodiment has advantages in terms of low cost construction. The eyelid configuration can be inexpensively fabricated by punching, eliminating the precision welding commonly required by pads of the slot type.

What is claimed is: g

1. In web treating apparatus having means for conveying a web along a path of movement therefor apparatus comprising:

a plurality of pressure pads of generally rectangular configuration in a plane facing said path, spaced along said path, and located on both sides of the path with their lengths disposed transversely relative to the direction of said path, each pad having an apertured substantially even surface facing the path, all of said apertured surfaces generally paralleling the path at a uniform distance therefrom;

said apertured surface of each pad having two rows of openings extending lengthwise of said surface and generally along its edges and separated by a longitudinal bisecting plane of said surface in spaced relation with either row, structure in said surface defining said openings of each row being aligned and arranged to discharge jets of air or other gas in a common oblique direction relative to, and free of, said surface toward said path and toward said bisecting plane; and

said openings of both rows being aligned, arranged, and sufficiently spaced to cause air jets issuing from one row of openings to pass to a substantial extent between jets of air issuing from the other row of openings of the same pad with impingement and intermingling of the lateral portions of jets of air from both rows of openings adjacent said web path sufficient to establish positive pressure regions of air having a measurable static pressure confined between a web traversing said path and said pad surface.

2. The apparatus of claim 1 wherein:

the openings of one of said rows of a pad are in staggered relation with the openings of the corresponding other row of said pad.

3. The apparatus of claim 2 wherein:

each of said eyelid openings are formed with a lid depending from said surface to define a space contiguous with the interior of the respective pad and a periphery of said opening comprising a straight portion parallel to the longitudinal sides of the pad rection of the path.

222 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 7, 5 Dated September 24, 1974 l t fl Alex .I. Schregenberger It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Page 1, Column 2, line 13,"ca.rryi.ng" should be --conveying-'-.

Page 1, Column 2, line 66, "pad" should be --and--.

Signed and sealed this 12th day of November 1974.

(SEAL) Attest:

MCCOY M.- GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. In web treating apparatus having means for conveying a web along a path of movement therefor apparatus comprising: a plurality of pressure pads of generally rectangular configuration in a plane facing said path, spaced along said path, and located on both sides of the path with their lengths disposed transversely relative to the direction of said path, each pad having an apertured substantially even surface facing the path, all of said apertured surfaces generally paralleling the path at a uniform distance therefrom; said apertured surface of each pad having two rows of openings extending lengthwise of said surface and generally along its edges and separated by a longitudinal bisecting plane of said surface in spaced relation with either row, structure in said surface defining said openings of each row being aligned and arranged to discharge jets of air or other gas in a common oblique direction relative to, and free of, said surface toward said path and toward said bisecting plane; and said openings of both rows being aligned, arranged, and sufficiently spaced to cause air jets issuing from one row of openings to pass to a substantial extent between jets of air issuing from the other row of openings of the same pad with impingement and intermingling of the lateral portions of jets of air from both rows of openings adjacent said web path sufficient to establish positive pressure regions of air having a measurable static pressure confined between a web traversing said path and said pad surface.
 2. The apparatus of claim 1 wherein: the openings of one of said rows of a pad are in staggered relation with the openings of the corresponding other row of said pad.
 3. The apparatus of claim 2 wherein: each of said eyelid openings are formed with a lid depending from said surface to define a space contiguous with the interior of the respective pad and a periphery of said opening comprising a straight portion parallel to the longitudinal sides of the pad and transversely of the web path, and a curvilinear portion extending from one end of the straight portion to the other.
 4. The apparatus of claim 1 wherein: said openings have an eyelid configuration.
 5. The apparatus of claim 1 wherein: said pads on one side of said path are arranged in staggered relation to said pads on the other side of said path.
 6. The apparatus of claim 1 wherein: said openings are of eyelid configuration; and said surface of each pad is convexly and slightly curved toward the web path in the longitudinal direction of the path. 